Add copilot chat plugin to leverage AI to answer user queries based on questions and answers

## Is your feature request related to a problem? Please describe

It's actually a proposal. I think it's very suitable to add AI ability to Apache Answer cause it's an QnA platform. I think we can implement it as a plugin but I'd like to put issue here for more audience. I've already done some POC, feel free to check below demo. Welcome any comments and discussions.

https://github.com/user-attachments/assets/28a848f2-77ee-4dec-9ed3-9dd06c65f21e

## Describe the solution you'd like

As showed in above demo.

There're also some changes needed in answer repo, e.g.
1. supporting some plugin configs depend on others, and only show when it's a specific value.
2. it could be a new plugin type, cause it needs pass the `syncer` and add some REST API for chats.

If it's accepted, I can also implement these as well as this plugin itself.

Comienza revisando el sistema de plugins de Apache Answer, el manejo de la configuración, la integración del syncer y la arquitectura de la REST API. El estado final propuesto incluiría un plugin de chat de Copilot aceptado, además de compatibilidad con la configuración de plugins dependientes y APIs de chat, pero el issue no identifica archivos, pruebas ni un alcance de implementación definido.

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